September 9-10, 2004
Salar Grande, Atacama Desert, Chile

Agenda
• Finalize fluorescence imaging protocol
• Test onboard spectrometer with foreoptic
• Work around failed power relays
• Drive autonomously

Status and Progress
Fluorescence protocol developed. We continue to have excellent results from Zoë’s onboard fluorescence imager (FI). After initial confirmation that the instrument is able to excite and detect fluorescence in daylight (under the shade of the rover), we have further refined the specific filter combinations and exposure times in order to reliably detect chlorophyll fluorescence with 450nm excitation working better than 350nm. Tests with sprayed water we found to significantly improve the fluorescence signal of chlorophyll containing organisms, perhaps simply due to removing dust. A DNA dye, which only fluoresces in the presence of DNA, was found to provide minimal enhancement perhaps due to the difficulty in penetrating the exterior coating of microorganisms.

Onboard spectrometer functioning. We have verified the onboard visible-near infrared (VNIR) (350nm-2500nm) is functioning properly through the 1° foreoptic mounted on Zoë’s pan-tilt mechanism. The pan axis makes a complete rotation, 360° and the tilt axis covers the sky (+20°) to almost straight down (-80°). This configuration allows Zoë to collect collect images but also spectra of targets anywhere in its vicinity. The interface electronics between the spectometer and Zoë’s computers become more stable as we refine the boot sequence, and as the protocol we use for collecting spectra gets more concrete we are better able to keep the device in proper dynamic calibration, specifically to maintain proper dark current measurements and white references (for changing light levels). A goal of this year’s field experiments is to get sufficient experience with rover-based VNIR to reliably collect spectra and have a working protocol to use in the future.

Replaced power relays. Further diagnosis will be required to understand exactly why Zoë’s main power relays are slowly failing, but a likely explanation is that the are unable to tolerate low voltage conditions that exist during low-power startup. The relays have an integral circuit that sets the voltage at which the relays pull in and that drops the current required to hold them, it seems that it is this circuit, not the relay itself that is failing. Our work around is a manual switch to turn off and on rover power. The implication is that Zoë will not be able to turn itself off and on.

Drove autonomously. We have conducted some initial tests in autonomous navigation, in the vicinity of base camp, to tune the camera models and traversabililty estimates. As expected, late day low-angle sun conditions have caused some difficulties but performance is generally good. In the coming days we will move to longer traverses out of camp.

Upcoming
• Exercise autonomous navigation
• Continue to refine position estimation
• Test autonomous mission planning and execution
• Prepare for first remote science experiments

Weather
Mornings: Light fog, still, moderate 11-13C, 70% humidity
Afternoons: Clear, some light breezes, warm 23-25C, 40% humidity
Evenings: Low fog, calm, warm 14C, 50-60% humidity

Quote of the Day
"We continue to enjoy spam in the Atacama"
"guru chunky whomsoever francine additional brouhaha"